1. Field of the Invention
The present invention relates to an LED (light emitting diode) current driving system. Particularly, the present invention relates to an LED current driving system for an LCOS (liquid crystal on silicon) display.
2. Description of the Prior Art
Referring to FIGS. 1A and 1B, schematic views of a conventional LED current driving system for an LCOS display are shown. Firstly, referring to FIG. 1A, the conventional LED current driving system 11 includes a timing controller 111, an LCOS panel 112, a transistor 113, and a resistor 114. The conventional LED current driving system 11 is used to control the current of a LED 115. The timing controller 111 is mounted on the LCOS panel 112 for providing a PWM (pulse width modulation) signal to the transistor 113 to control whether the transistor 113 is conducted. According to the ON/OFF states time of the transistor, the magnitude of the current flowing through the LED 115 is controlled.
Referring to FIG. 1B, the conventional LED current driving system 12 is applied in a color sequential LCOS display. The LED current driving system 12 includes a timing controller 121, an LCOS panel 122, three transistors 161, 171, 181, and three resistors 162, 172, 182. The conventional LED current driving system 12 is used to control the currents of three LEDs (red, green, and blue LEDs) 13, 14, 15. The timing controller 121 in addition to providing a PWM signal to the transistors 161, 171, 181 also provides the ON/OFF timing, so that three LEDs 13, 14, 15 can be conducted sequentially to achieve a color sequential control.
The conventional LED current driving system does not integrate all the elements, so the pin number of the LCOS chip, the overall area, and the system cost are increased. Moreover, as the integration is not satisfied, the yield of the LED current driving system may be affected. Besides, the conventional LED current driving system cannot stably and precisely control the current flowing through the LED, so that the color quality is poor.
Therefore, it is necessary to provide an LED current driving system, so as to solve the above problems.